Inner chainring rubbing chainstay

[niloc]

I recently replaced the cup/cone bottom bracket of my wife's bike with UN54 of the same length (127mm). But the inner chainwheel of her 25 year old Sugino chainset is now rubbing on the chainstay. The bike has not had exceptional use so I think the chainset is still ok but it might not be JIS taper. BB axles don't seem to come much longer than 127mm. So can anyone suggest a solution, eg. where to get a BB spacer?

[BigG]

Try ebay. I have bought 1 mm and 2 mm spacers from ebay suppliers in the past.

[Redvee]

Look for freewheel spacers, should be more readily available given the popularity of fixie & single speed bikes.

[Brucey]

any LBS will have the spacers that sit by sturmey archer 3speed sprockets. These work fine.

cheers

[Mick F]

I'm sure a spacer would work, but it isn't the answer to the problem.

It probably is like OP niloc says, the original BB wasn't JIS.

Unless it's too late to take the BB back, fine - go with the spacer. If you can take it back, get an ISO instead.

[Brucey]

if the BB is replaced with an ISO the spindle (being narrower at the end, not fatter, than JIS) would have to be longer again in order to keep the chainring clear of the chainstay, woudn't it?

BTW not all 127mm long spindles are created equal.

BB spindles come symmetric or asymmetric in the same length. Modern ones tend to be symmetric so very often a longer symmetric spindle is the correct replacement for an older shorter asymmetric spindle, since this will put the chainline further out (where it needs to be ) vs a one of the correct length that is symmetric.

Sheldon Brown has some details of different spindles, as does the SJS website.

cheers

[Mick F]

if the BB is replaced with an ISO the spindle (being narrower at the end, not fatter, than JIS) would have to be longer again in order to keep the chainring clear of the chainstay, woudn't it?

Not necessarily - I think!

..... or am I looking at this the wrong way round?

[531colin]

Sheldon says

If you install an ISO crank on a JIS spindle, it will sit about 4.5mm further out than on an ISO spindle of the same length. http://sheldonbrown.com/bbtaper.html

[Mick F]

Ah.
That makes sense, so I did have my head on the wrong way round then!

Therefore, what is wrong with the OPs chainset and BB?
The UN54 is JIS, so even if the Sugino chainset was ISO, it would fit further out.

I suppose it was ok before?
Therefore it must be something to do with the symmetry of the new BB.

[niloc]

Look for freewheel spacers, should be more readily available given the popularity of fixie & single speed bikes.

any LBS will have the spacers that sit by sturmey archer 3speed sprockets. These work fine.

Will these fit over the drive side thread of a UN55 bottom bracket?

[Brucey]

any LBS will have the spacers that sit by sturmey archer 3speed sprockets. These work fine.

Will these fit over the drive side thread of a UN55 bottom bracket?

yup

cheers

[cycleruk]

I used an aluminium spacer from an old cassette, with the internal spigots filed off, placed between the BB and shell.

[Redvee]

Look for freewheel spacers, should be more readily available given the popularity of fixie & single speed bikes.

Will these fit over the drive side thread of a UN55 bottom bracket?

Again, yes. The thread on a freewheel is 1.37"x24tpi, a traditional BB thread is 1.37"x24tpi.

[rich100]

Hi

Sorry to hijack the thread....

I have pretty much the same issue, I've fitted a px50 chainset (bought s/h off here) and fitted it to a 127mm un55, pretty sure it's a JIS bb will see if i've got the box still). However the chainring bolts are scraping the paint off the chainstay it's that close when fully tightened up, probably because the rear stays have been spread to take a 130mm hub.

So, if I fit one these spacers on the drive side, will it affect the non drive side lock ring? or is it plenty long enough to engage the bottom bracket. Also, if spacing it off, that means the cranks will be offset to the right slightly, I'm guessing that a few mm will make no difference to comfort??

Also, if i could bother someone for a link to the right product (shop or ebay I don't mind) I would be gratefull.

Thanks

[Brucey]

re the LH side; it depends what model BB you have as to whether you can fit a spacer on the right or not.

cheers